Technical Specifications:

Basic Properties (26K PDF)
Pressure-Temperature Chart (468K PDF)
Thermodynamic Properties (ENG) (162K PDF)
Thermodynamic Properties (SI) (1M PDF)
Pressure-Enthalpy Chart (ENG) (279K)
Pressure-Enthalpy Chart (SI) (359K)
Technical Data Sheet (77K PDF)
MSDS

Forane® 408A refrigerant (R-408A) is a low-ozone depleting, near-azeotropic HCFC blend of R-22, R-125, and R-143a that was designed to match the performance of R-502.

Application:
R-408A is a retrofit solution for medium and low temperature refrigeration systems that are currently using R-502.  R-408A should not be mixed with R-502 or used to top off the charge of an existing system operating on R-502.

R-408A is not intended for use in new equipment.  Refrigeration applications that were previously designed to use R-502 can now be specified to use a long-term alternative HFC blend, such as R-404A.  Manufacturers have developed new R-404A compressors and refrigeration systems for use in food display and storage cases, cold storage rooms, ice machines, transportation, and process refrigeration.

Properties & Performance:
When retrofitting from R-502 to R-408A, system capacity and efficiency often improve.  Both low and high side pressures are nearly identical for R-502 and R-408A.  An increase in head pressures of 5 psi may be seen in high ambient environments with R-408A.

Lubrication:
R-408A can be used with mineral oil, alkylbenzene, or POE lubricants.  Systems operating with R-502 and mineral oil and showing adequate lubricant return to the compressor may continue to use mineral oil with
R-408A.  Alkylbenzene and/or POE may be used alone or in combination with mineral oil in order to improve lubricant miscibility and return to the compressor.  Consult manufacturer's guidelines for additional recommendations.

Charging:
Due to the zeotropic nature of the R-408A blend, it should only be charged as liquid to prevent fractionation (changes in designed refrigerant composition). In situations where vapor would normally be charged into a system, a valve should be installed in the charging line to flash liquid from the cylinder into vapor. Charging weight ratios of R-408A are typically 85-90% of the charge weight of R-502.

Retrofit:
System components (TXVs, line sizes, compressors) offer similar performance with R-502 and R-408A and usually do not requre changing when retrofitting.

Retrofit Procedure

1. Establish baseline performance. Note the oil type in use and any system operating data (if system is operating properly). Check for existing leaks and identify any needed repairs.

2. Recover the existing refrigerant charge (DO NOT vent to atmosphere). Weigh the amount of refrigerant removed.

3. Perform any repairs identified in step 1 and fix any leaks. 

4. Replace the filter-drier and, if necessary, elastomeric seals (O-rings, sight glasses, etc.). Verify the condition of the system oil; replace if necessary.

5. Evacuate the system (less than 500 microns) and ensure it maintains a vacuum. If vacuum is lost, it may indicate that leaks are present in the system.

6. Charge system with R-408A refrigerant. Remove refrigerant as liquid only from cylinder. The charge ratio should be approximately 85-90% of the charge weight for R-502.

7. Adjust TXV set-point and/or refrigerant charge to achieve the desired superheat.

8. Monitor oil level in the compressor. If necessary, adjust oil amount to attain normal operating level (mid-sight glass).

9. Label system clearly, indicating the type and amounts of system refrigerant and oil.

PropertiesR-408A
Average Molecular Weight (g/mol)87.0
Normal Boiling Point (°F)-48.2
Critical Temperature (°F)181.7
ASHRAE Safety Group ClassificationA1
Ozone Depletion Potential (ODP)0.026
Global Warming Potential (GWP)3,152